1. Field of the Invention
The present invention relates to an optical disk system. More particularly, it relates to an apparatus for adjusting a tracking signal used for a tracking servo control to ensure stable operation of the tracking servo control for a variety of different optical disks.
2. Description of the Related Art
Both focus servo control and a tracking servo control must be carried out in an optical disk system. The focus servo control adjusts the position of an object lens to focus a beam emitted from a laser diode onto a track of an optical disk, so that any beam displacement at the track caused by an eccentricity in the motion of the optical disk and/or any deformation of the optical disk can be compensated. The tracking servo control adjusts the position of the read/write head to ensure that the head follows the track, to obtain a fine, or precise control of the position of the head.
Various different optical disks are used in an optical disk system and the tracking servo control is effected by using a light reflected from a groove formed in the optical disk. However, this reflected light is varied in response to the change of an exposure light used for data read and data write operations, dispersion of the groove shape due to differences between manufacturing lots and differences in manufacturing techniques, and differences in a groove shape, for example, a difference between a U-shaped groove and a V-shaped groove. In a prior art tracking servo control system, compensation for a differing reflection light due to differences between a write data exposure light and a read data exposure light is known, since the tracking servo control system receives a write mode signal and a read mode signal. However, in the prior art tracking servo control system, compensation for the dispersion of the groove shape is not yet practiced, and as a result, a fine or precise position control can not be fully carried out. In addition, compensation for differences in the groove shape is not practiced, and as a result, the optical disk system of the prior art can not use different types of optical disks having various groove shapes.